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EV motor is ‘first’ to avoid the use of ‘heavy’ rare-earths

13 July, 2016

Two Japanese companies – Honda and Daido Steel – claim to have developed the world’s first practical “hot deformed” neodymium magnets that contain no “heavy” rare-earth materials, yet offer good temperature resistance and the magnetic performance needed for use in electric vehicles (EVs). The new magnets will be used for the first time in Honda’s new Freed hybrid vehicle, which is due to go on sale later this year.

Demand for neodymium magnets, which are used widely in EV motors, is expected to grow exponentially. Until now, however, “heavy” rare-earths – such as dysprosium or terbium – have had to be added to these magnets to allow them to be used in high-temperature environments. Supplies of these elements are limited and their use carries risks in terms of procurement and costs. Reducing their use has been a major challenge for EV manufacturers.

Daido Electronics – a subsidiary of Daido Steel – produces neodymium magnets using a method called hot deformation, rather than the more common sintering technique. The magnets contain nanometer-scale crystal grains that are about ten times smaller than those in sintered magnets, making them more resistant to high temperatures.

Daido is now using hot deformation to produce magnets that contain no heavy rare-earths, and Honda has designed a new motor based on these magnets. The shape of the rotor has been revised to optimise the flow of the magnetic flux. Honda claims that the motor offers torque, output and heat resistance performance equivalent to those using magnets containing heavy rare-earths.

A rotor designed for the Honda motor that uses magnets containing no "heavy" rare-earth materials

Next month, Daido Electronics will start to mass-produce the new magnets on a production line built with support from the Japanese Ministry of Economy, Trade and Industry. It is continuing to develop the technology further, and is working with a Canadian supplier of magnetic powders, Magnequench International, to develop new types of powder with enhanced magnetic properties.

Honda plans to use the rare-earth magnets in a new hybrid drive system that it will use initially in the Freed and later in other models.

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